One thing for sure there are as many different ways to create driver command inputs to the PCM (powertrain control module) as "you engineers" (VBG) can think of, and as I a tech I have to understand and react to every one of them.
Most of the cars in the last ten years use a fairly linear TPS sensor. While inside the PCM it may well work in steps to a degree, as a tech with a scan tool I see both throttle position sensor voltage as well as throttle opening percentages. Most of the cars learn a closed throttle position on key on, and unless there is an issue that causes a TPS voltage that is lower than the original closed throttle, the closed throttle position will always report a 0-1%. (99.9 percent of the time) The one thing the the PCM does with the TPS more than anything else is respond to sudden movement. That's why a poor connection, or a sensor that is wearing out and having voltage drops/spikes drives the system crazy. The biggest thing about OBDII is that it isn't a diagnostic system for technicians, it's an emissions program. The vehicle by design is supposed to adjust itself to get the lowest emissions possible, and then test to make sure it's working. To achieve the lowest possible emissions, it needs to keep air fuel ratios in tight check. (Long term trim, short term trim, and rear trim) and then continue the adjustments to reduce fuel consumption and increase fuel mileage as much as possible, VCT (variable cam timing), EST (electronic spark timing).
Now spark timing maps, they are all over the place as far as what input has more authority over another between engine platforms. The thing is, no-one else even considered "fly by wire", or computer controlled throttle actuators. Between the computer having complete direct throttle control, MAF (mass air flow) sensor inputs, RPM, CTS (coolant temperature) , VVCT (variable cam timing), KS, (knock sensor), it only goes to figure that the PCM will learn, and then continue to re-learn as the filter gets dirtier. What makes this neat is you could have positive feedback for any actual change in the required throttle position for any type of a cruise demand as you played around with different air filter restrictions.
So can you guess where this is going?
It is not at all beyond comprehension that the PCM's programming could be written to alert a technician about whether an air filter actually required replacement or not. Everything is already there, it's just a matter of writing the code.